Overflow trap for manometer



United 8tates Patent C? F OVERFLOW TRAP FOR MANOMETER Wilfred R. Valcourt, Seattle, Wash., assignor to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Filed Apr. 7, 1959, Ser. No. 804,700

3 Claims. (Cl. 73-401) This invention relates to a manometer system and more particularly to a novel means for providing an overflow trap for the system.

When a manometer is used to measure pressure, there is often a surge of pressure which will force the working fluid of the manometer, usually mercury, completely out of the manometer tube. The prior art shows various means to prevent this; for example, means are used either to block the flow of mercury above a certain point in the tube or to provide diflerent types of overflow traps for the mercury.

There are diificulties with the prior art solutions. For instance, when the mercury is blocked in the tube, the surge of pressure is not relieved, but the manometer tube remains under a pressure higher than its normal working pressure. When a prior art manometer trap is used, the mercury sometimes flows immediately back into the tube; and, if the excess of pressure has not been relieved, the mercury will again be forced up the tube, thereby causing a bubbling or splashing action of the mercury. In still other prior art solutions the mercury passes through tubes or valves into a manometer trap from which the mercury may be poured back into the manometer tube or from which there is valving or tubing means to return the mercury to the manometer tube; this involves certain complexities of safely returning the mercury to the manometer tube.

An object of my invention is to provide an overflow trap so that when there is an increase of pressure in the manometer tube which would push the manometer fluid above its normal working level, the mercury from the manometer tube will be retained in an overflow reservoir until the pressure increase is relieved.

Another object of my invention is to provide for the return flow of the manometer fluid simply by moving the manometer tube relative to the overflow reservoir, thereby exposing an opening in the manometer tube to the mercury stored in the overflow reservoir, thereby eliminating any additional tubes or valves or pouring devices, and thereby increasing the ease and safety with which the mercury may be returned to the tube.

A further object of my invention is to provide an overflow reservoir positioned around the manometer tube thereby eliminating any additional tubing or valves or pouring devices.

Figure 1 shows an embodiment of my invention in which the overflow opening in the manometer tube may also be used as the return opening and in which the manometer tube is open to the atmosphere.

Figure 2 shows a second embodiment of my invention in which an additional opening is provided in the manometer tube to act as a return flow opening and in which the overflow reservoir is not exposed to the outside atmosphere, so that a pressure diflerent from atmospheric pressure may be maintained in that portion of the manometer tube about which the overflow trap is located.

I shall noW describe the first embodiment of my invention, which is shown in Figure 1. There is a manom- 2,950,867 Patented Nov. 22, 1960 eter tube 2, having a passageway 3 for containing a working fluid such as mercury. The tube 2 is encircled by an overflow trap, generally designated as 4. In the upper portion of the manometer tube 2, and above the normal working level of the mercury, is an overflow opening 6, which leads from the passageway 3 to an overflow reservoir 8, which has a containing surface 9. The top of the passageway 3 is blocked by a baflle 10 to prevent the mercury from going out the end of the tube 2, which baflle 10 extends beyond the edges of the manometer tube 2 to prevent splashing of the mercury out of the overflow reservoir 8. The overflow reservoir 8 is shown as a right circular cylinder with a cylindrical wall 12 and a flat base 14. Additional baffles 15 may be extended from the upper portions of the cylinder wall 12 which also prevent splashing of mercury out of the overflow reservoir 8.

An opening 16 is provided in the flat base 14 so that the manometer tube 2 may extend through the flat base 14 and into the overflow reservoir 8. A tubular wall 18 connected to the base 14, which wall 18 defines the opening 16, extends downward from the base 14 to accommodate the sealing means, generally designated as 20. The sealing means 28 performs the dual function of preventing flow of mercury between the tubular wall 18 and the tube 2, and of holding the overflow trap 4 securely in a position relative to the manometer tube 2. The sealing means 20 consists of an O-ring 22 fitting around the tube 2, a flanged edge 24 on the tubular wall 18 to fit against the O-ring 22, aninternally threaded nut 26 to fit over the flanged edge 24 and to engage an externally threaded nut 28, so as to be able to compress the O-ring 22 between the flanged edge 24, the externally threaded nut 28, and the tube 2, thereby sealing the opening 16 and providing a friction fit against the tube 2. When the sealing means 20 is to be securely fixed to the tube 2, the externally threaded nut 28 is screwed into the internally threaded nut 26, thereby compressing the O-ring 22. When it is desired to loosen the sealing means 20, the externally threaded nut 28 is screwed out from the internally threaded nut 26, thereby relieving the compression on the O-ring 22.

In operation, the manometer tube 2 extends through the opening 16 and through the overflow reservoir 8, and the sealing means 20 is made tight around the manometer tube 2 and so positioned that the opening 6 in the manometer tube 2 is located in the upper part of the overflow reservoir 8. This is the working position of the overflow trap 4, which working position is shown in Figure 1. When there is a surge of pressure in the manometer tube 2 so as to drive the mercury above the normal working level in the tube 2, the mercury will strike the baffle 10 and will flow out the overflow opening 6. The overflow reservoir 8 is of suflicient capacity to contain all of the mercury in the manometer tube 2. When all the mercury has passed through the overflow opening 6 and into the overflow reservoir 8, the gas or fluid Whose pressure is being measured will pass out through the overflow opening 6 and harmlessly into the atmosphere. When the pressure surge is relieved and it is desired to return the mercury to the manometer tube 2, the sealing means 20 is loosened slightly so that the sealing means 20 may be slidably moved along the tube 2, but still maintain enough compression in the O-ring 22 to maintain a seal between the wall 18 and the tube 2. The manometer tube 2 is slid down through the overflow reservoir 8 until the overflow opening 6 is positioned very close to the opening 16. The mercury may then flow from the overflow reservoir 8 through the overflow opening 6 and back into the manometer tube 2. The manometer tube 2 is then raised to its previous position with the overflow opening 6 high in the overflow reservoir 8, and the sealing means 20 is tightened so that the overflow trap 4 is again held firmly in working position.

I will now explain the second embodiment of my invention, shown inFigure 2. There is a manometer tube 32, having a passageway 33 for containing a working fluid such as mercury. The tube 32 is encircled by an overflow trap generally. designated as 34. In the upper portion of the manometer tube 32, and above the normal working level of the mercury, is an overflow opening36, which leads from the passageway 33 into an overflow reservoir 38, which hasa containing surface 39. The passageway 33 is blocked by a plate 49, positioned. inside the tube 32 and immediately above the opening 36, so that mercury will not proceed further upthe passageway 33 than the plate.40. The overflow reservoir 33 is shown as a right circular cylinder with a cylinder wall 42 and two flat bases 44. An opening 46. isprovi ded in each ofthe flat bases. 44 so that the tube 32 may extend through and beyond each of the flat bases 44 and thus through the overflow reservoir 38. Tubular walls .48 which define the openings 46 are connected to the bases 44 and extend away from the overflow reservoir 38 to accommodate sealing means generally designated as 28, which seal both openings 46. Each of the sealing means 29 performs the functions of preventing flow of mercury or gas be tween the tube 32 and the tubular walls 48, and also of holding the overflow trap securely in a position relative to the manometer tube 32. Each of thesealing means 20 consists of an O-ring 22' fitting around the tube 32, a flanged edge 24 on the tubular wall 48 to fit against the O-ring 22', an internally threaded nut 26' to fit over the flanged edge 24 and to engage an externally threaded nut :28, soas to be able to compress the O-ring 22' between the' flanged edge 24', the externally threaded nut 23',

.and the tube 32, thereby sealing the opening 46 and providing a friction fit against the tube 32. The top sealing means 20 is provided to seal the upper opening 46. An intermediate sealing means 20 is provided to seal the lower opening 46. The bottom sealing means 20 is provided to retain any mercury which may be blown out through the return flow opening 50. The return flow opening 50, leading from the passageway 33, is provided in thetube 32 below the overflow opening 36, such that when the overflow opening 36 is positioned in the upper portion of the overflow reservoir 38, the return flow opening. 50 is positioned just below the intermediate sealing means .20. The two externally threaded nuts 28' of the intermediate and bottom sealing means 2% are. connected by a flange 52 toform one integral part,

which is a double-ended externally threaded nut, generally designated at 54, so as to make an enclosed passageway between the intermediate and bottom sealing means 2-0, so that the return flow opening 50 does not communicate with. the outside atmosphere. The tubular wall 48 located in the bottom sealing means 20 is not connected to any overflow reservoir but merely functions as a part of the bottom sealing means 20' to compress'the O-ring 22'. There is a third tube opening 56 provided in the tube 32 to communicate with that portion of the passageway 33 above the plate .40. When the overflow opening 36 is positioned in the working position, i.e., in the upper portion ofthe overflow reservoir 38,-the third opening 56 is just below the top sealing means 20', so that the third opening 56 communicates with the interior of the overflow reservoir 38 and with the overflow opening 36, but

not with the outside atmosphere. Thus neither the third opening 56 nor the overflow opening 36, nor the return flow opening 50 communicate with the outside atmosphere. ends of the passageway 33 of the tube 32, so that the ends of the. tube 32 may be connected to two diflerent pres- Therefore a pressure may be maintained at the suresources, and the difference in the pressures may be measured. The tubular wall 48 of the top sealing means 20' fits loosely enough about the tube 32 to allow the free passage of air from the third opening 56 to the overflow opening 36.

The overflow trap 34 is shown in its working position in Figure 2. The operation of the apparatus of Figure 2 is substantially the same as the operation of the embodiment of Figure l, and therefore this operation will be explained only briefly. After there is a surge of pressure in the tube 32 and the mercury flows through the overflow opening 36 and into the overflow reservoir 38, all three sealing means 2%) are slightly loosened and the tube 32 is raised so that the return flow opening 50 is positioned at the lower opening 46. This allows the mercury in the overflow reservoir 38 to flow through the return flow opening 50 and back into the manometer tube 32. The manometer tube 32 is then returned to its working position, i.e., with the overflow opening 36 in the upper portion of the overflow reservoir 38, and with the return flow opening 50 betweenthe two lower sealing means 20'. The bottomv sealing means 20 is provided to catch any mercury which may splash out of the return flow opening 50. To return any such mercuryWvhich may splash out the return flow opening 50, the manometer tube 32 is merely lowered so that the returnflow opening 50 is very close to the bottom sealing means 20', so that the mercury will flow through the return flow opening 50 and into the manometertube 32. i

Since numerous changes may be made in the above apparatus and different embodiments may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing descrip tion or shown in the accompanying drawings shall be interpreted as illustrativeand' not in a limiting sense.

I claim as my invention: 7

1. In an overflow trap'fo-r a manometer, the combination comprising, a reservoir for'storing overflow fluid and having an operu'n in the bottom thereof, a manometer tube havingan overflow opening above thenornial working level of fluid in said manometer tube, said manometer tube being disposed within the opening in the bottom'of said reservoir and being moveable so that the position of the overflow opening may be adjusted relative to the level of fluid insaid reservoir, and sealing means for providing a fluid seal between said manometer tube and the openin in the bottom of said reservoir.

2. A tube having a passageway to receive a fluid, an overflow opening inthe tube disposed above the normal working level of said fluid, said overflow opening'leading from the passageway to an overflow reservoir, 'said reservoir beingmoveable relative to the tube, along the longitudinal axis of said tube, so that the reservoirs position may be adjusted relative to the overflow opening, a return flow opening in the tube located below the overflow opening, arr opening in said reservoir to accommodate the tube, sealing means positioned relative to the reservoir opening and the tube so as to seal said reservoir opening, said sealing means'being moveable so'as to be able to be positioned above or below the return flow opening in the tube.

i 3. The combination as claimed'in. claim 2, a second sealing means positioned relative to the reservoir and the tube, so as to enclose the reservoir so that the reservoir communicates only with the passageway in the tube.

1,840,748 Star Jan. 12, 1.932 

